The present invention relates to an apparatus having a plurality of replaceable parts each having a particular service life and, more particularly, to an electrophotographic image recording apparatus.
Various parts constituting a single apparatus each has a particular rate of composition, i.e. a service life. Assume an apparatus in which all the parts are individually fixed in position and not removable from the apparatus. Then, when one of the parts whose life is shortest fails to serve the function assigned thereto, the apparatus has to be bodily discarded or needs a thorough overhaul despite that the other parts having comparatively long lives are still usable. A current trend in various fields is, therefore, toward an apparatus which is constituted by a plurality of replaceable parts. Especially, in the electrophotographic imaging art, a printer, facsimile machine, copier or similar image recording apparatus made up of a plurality of replaceable parts each having a particular life has been proposed in various forms. In an electrophotographic copier, for example, various replaceable parts such as a main charger, toner cartridge, developing unit, transfer charger and a cleaning unit which are different in life are arranged around a photoconductive drum. These parts each is determined to have reached its life and replaced when the copier has been operated for a predetermined period of time or has produced a predetermined number of copies, i.e. a running number. For example, the life in terms of the running number is predetermined to be 1,000 for the toner cartridge, 4,000 for the developing unit, 8,000 for the main and transfer chargers, 16,000 for the cleaning unit, and 32,000 for the drum. More specifically, the lives each is an integral multiple of the life of the toner cartridge which is shorter than the others. Hence, before the drum is replaced once, the cleaning unit, main and transfer chargers, developing unit and toner cartridge have to be replaced twice, four times, eight times, and thirty-two times, respectively. Such replaceable parts are removably mounted on an apparatus body independently of one another (e.g. Japanese Patent Laid-Open Publication No. 166960/1985). This kind of scheme has a drawback that used parts have to be removed from the apparatus body and replaced with new parts one by one, resulting in inefficient replacement. Moreover, it is likely that the operator forgets to remove some of the used parts from the apparatus body.